The Army is investigating members of a Reserve unit in Iraq who refused to deliver a fuel shipment to a town north of Baghdad under conditions they considered unsafe, the Pentagon and relatives of the soldiers said Friday. Several soldiers called it a "suicide mission," relatives said.

Up to 19 members of the 343rd Quartermaster Company were detained at gunpoint for nearly two days after disobeying orders to drive trucks that they said had not been serviced and were not being escorted by armed vehicles to Taji, about 15 miles north of Baghdad, relatives said after speaking to some of the soldiers.

The mission was ultimately carried out by other soldiers from the 343rd, which has at least 120 soldiers, the military said.

Jackie Butler of Jackson, Miss., the wife of Staff Sgt. Michael Butler, 44, said she had been awakened at about 5:30 or 6 a.m. Thursday by a call from an officer from Iraq. He told her "that my husband was being detained for disobeying a direct order," Butler said, "and he went on to tell me that it was a bogus charge that they got against him and some of those soldiers over there, because what they was doing was sending them into a suicide mission, and they refused to go."

A senior Army officer in Washington said that 19 soldiers from the unit had been assembled Wednesday morning to deliver fuel but that some had refused to go. He denied they had been held under guard.

The officer, speaking on condition of anonymity, said the soldiers had raised "some valid concerns."

"Unfortunately it appears that a small number of the soldiers involved chose to express their concerns in an inappropriate manner," he said. Insubordination during wartime is considered a grave offense, and an inquiry is under way, the officer said, to determine whether the Uniform Code of Military Justice was violated and whether disciplinary measures were warranted.

It is unclear whether this is the first time a sizable group of soldiers in Iraq has refused to carry out orders, and the military is playing down the mutiny as an isolated incident. But the small rebellion suggests that problems linger with outfitting soldiers with adequate equipment in an increasingly dangerous country.

"I know soldiers are deeply concerned and have been deeply concerned about the equipment shortages," said Paul Rieckhoff, a veteran of the Iraq war and executive director of Operation Truth, a New York advocacy group working to draw attention to the needs of soldiers in Iraq and returning veterans.

The incident, which was first reported in the Clarion-Ledger in Jackson, Miss., where several of the soldiers live, apparently began after the company tried to deliver a shipment of fuel to a base but was turned away because the fuel was unusable, according to family members of some soldiers.

According to relatives and the Army officer, they returned to their home base in Tallil, where they were told to go to Taji to deliver the fuel. The group refused, citing the poor condition of their vehicles and the lack of an armed escort, family members said. American convoys, which are usually accompanied by armored cars and sometimes also by aircraft, are often attacked by insurgents.

"Yesterday, we refused to go on a convoy to Taji," Spc. Amber McClenny, 21, said in a message she left on the answering machine of her mother, Teresa Hill, in Dothan, Ala. "We had broken-down trucks, non-armored vehicles. We were carrying contaminated fuel."

After the soldiers were released, McClenny called her mother again and explained that the jet fuel the convoy had to carry had been contaminated with diesel and that because it had been rejected by one base, it would most likely be rejected by the Taji base they were ordered to go to.

Taji is in the volatile Sunni-dominated swath of Iraq, and Hill said her daughter felt "that if you go there, it's a 99 percent chance you will be ambushed or fired upon."

"They had not slept, the trucks had not been maintained, they were going without armed guards -- it was just a bad deal," Hill said. "And that's when whole unit said no." She said their defense is "cease action on an unsafe order."

Before the incident, relatives said, soldiers had complained to them that the equipment they had was shoddy and put them in greater danger. The relatives said they did not know whether such complaints had been made to the unit's command.

"He said, we go out on these missions, you know he was afraid they were going to break down, that they were no good, they were just piecemealing something together, and set up for people to come ambushing you," she added.

The senior Army officer said the military was investigating the issues of vehicle maintenance.